A blower of the type of the present invention is known from German patent specification DE 198 41 762 C2 and has proved useful in practice.
Double-flow radial blowers, as they are known, are employed to an increased extent in many domestic applications, for example in air conditioning applications and in other sectors. Double-flow means that the radial blower possesses two inlet ports which are located on axially opposite sides of the blower. Such a double-flow is also described as a preferred version for the blower described in DE 198 41 762 C2. In this case, an electric motor is used, which is mounted in a vibration-insulating manner on both sides in an elastic element. The connecting cable, coming from the engine, is routed through a partially hollow shaft, via a carrying arm, to a terminal box belonging to the housing subassembly. The electric motor is an alternating current motor which is designed as a closed external rotor motor. In the terminal box, the ends of the connecting lines of the motor are connected, and both connecting lines have an operating capacitor and fuses and also a connection terminal strip for the pluggable connection of a motor connecting cable are accommodated in the terminal box.
The object on which the present invention is based to provide a blower of the generic type described above, which, as compared with the known blower, has a marked reduction in weight and can convey at least the same air quantity while having a lower energy consumption. At the same time, the noise values of the blower in accordance with this invention should also not increase. This object is connected with the requirements of legislators and consumers for improved mass/power ratios of blowers of this type.
The object is achieved, according to the invention, in that the electric motor of the fan subassembly is an electronically commutated direct current motor (referred to, further, as an EC motor).
The electric motor according to the invention is therefore a brushless direct current machine in which the rotor has permanent magnets and the stator has a plurality of magnet coils. The stator may, in particular, be of three-phase design. The coil windings of the stator are connected, for electronic commutation, via a bridge circuit, in which transistors, such as preferably metal oxide semiconductor field-effect transistors (MOSFET) or bipolar transistors with an insulated gate electrode (IGBT), may be used. Particularly in the case of lower powers, the circuit may be designed as an integrated circuit (power IC), and therefore we may also speak of conversion electronics. These electronics constitute essentially a three-phase regulator, such as is also used in a similar way in frequency converters, so that the electric motor can be fed with direct voltage. Since such electronics can also additionally fulfill other functions, especially “control electronics” will be used further herein in this respect.
By means of the blower according to the invention, advantageously, because of the high motor efficiency and its compact type construction, higher powers can be achieved in the case of identical construction volumes and markedly reduced masses, as compared with a known blower, or identical powers can be achieved in the case of lower construction volumes and masses.
The motor may in this case have a rigid shaft, in the same way as the alternating current motor of the known blower, the stator of the motor being fixed on the shaft. According to the invention, therefore, it is likewise an external rotor motor, of which the shaft ends on both sides can be fastened in carrier elements of the blower.
In this case, as mentioned in the introduction, a drive decoupling serving for reducing solid-borne sound and bearing noises may take place in an appropriate way via elastic elements, such as elastomeric parts which are attached to the shaft via a fixing part. Thus, by virtue of the comparatively very low-mass EC motor, a very good decoupling result can be achieved.
As also illustrated in detail by the drawings of the invention, the blower according to the invention may advantageously be constructed in a modular manner, in which case the individual basic elements can be assembled simply by being plugged together and snapped or screwed to one another. The assembly times can thereby be kept extremely short.
According to the invention, as regards the electronic commutation, there may be provision for the motor to be sensor-controlled, in which case the position of the rotor is detected by at least one magnetic, electrical or optical position sensor, for example a hall sensor, a magnetoresistor or a potentiometer.
It is particularly preferable, however, to use such an EC motor which is controlled without a sensor, the position of the rotor being detected by means a counter voltage induced in the stator, and this countervoltage being used, via correspondingly treated signals, for fixing the commutation time points.
The counter voltage is linearly dependent on the motor rotational speed and on the exciting intensity and can therefore also be used to set the rotation speed exactly. Further, therefore, there is advantageously the possibility of utilizing this and other control and regulating functions of the EC motor in the blower according to the invention. The additional advantage, as compared with a sensor-controlled EC motor, is, in position detection via the countervoltage, also that there is no need to use position sensors which are sometimes susceptible to faults.
In EC motors, the control electronics are usually integrated into the motor and, depending on the power of motor, can be of corresponding size. In this case, these electronics, which are not required in alternating current motors, are located typically in the intake region of the blower, because sufficient cooling can also take place there due to the sucked-in air, so that a prescribed operating temperature is not overshot. To be precise, cooling is absolutely necessary for the functioning capacity of the electronics. As a result, however, a certain obstruction is caused in the intake region of the blower and, precisely in the case of blowers having double-sided suction, may give rise adversely to an uneven distribution of the sucked-in air.
In an advantageous embodiment of the invention, therefore, there may be provision for control electronics to be accommodated, separately from the EC motor, in a terminal box, as is also known from the prior art in the case of alternating current motors, although, there, with the exception of the motor connections, the operating capacitor, etc. Since the electronics are arranged at a spatial distance from the motor in the terminal box, unfavorable mutual influences are prevented, and the motor and electronics components supplement one another optimally.
In particular, an electronic module to be cooled specially, that is to say, essentially, a circuit board, on which the control electronics are arranged or connected, may be insertable into a clearance of the terminal box or onto a plug location on the underside of the blower. A cooling body of the electronic module may in this case project into a corresponding clearance on the lower housing shell and thus be in direct contact with the airstream inside the blower. By action being exerted by the blower air, an optimal flow around the cooling body takes place, but without the blower internal volume at the same time being reduced or the air stream disturbed.
Since there is then no need to ensure temperature limitation in the motor due to electronic components, a higher intrinsic heating of the motor may be permitted on account of the separation of the motor and electronics, to be precise, for example, an intrinsic heating, such as arises pursuant to the admissible thermal load upon materials used for insulating the motor.
The stator of the EC motor may in this case be encapsulated, completely, by means of a pour-around (or potting) material, preferably a thermosetting plastic, with the result that an optimal discharge of heat from the motor can be achieved and all the current-carrying parts are insulated and protected from contact.
In such an encapsulation of the stator, the rotating rotor may, in contrast to the known direct current motors, be designed not as a closed bell, but so as to be open on both sides on the end faces. Despite of such an open rotor, however, a high IP protection class can be achieved because the stator is encased on all sides. As is known, this IP protection class is understood to mean, according the standard EN 60529, the degree of protection with respect to contact, foreign bodies, such as dust, and moisture. The orifices in this case have the effect that the air conveyed by the blower flows around the stator, and at the same time it is also routed through the gap usually present between the rotor and stator, thus counteracting in advance an excessive heating of the motor components.
Further, owing to the described spatially separated combination of the EC motor and electronic module, an adaptation of the blower according to the invention to the most diverse possible customer interfaces is also possible quickly and simply. A preferred field of use in this case are fume extractor hoods, where the blower according to the invention can be used. In this field in particular, blowers with closed alternating current motors have hitherto being employed on account of the moist and often greasy exhaust air. In this respect, the invention constitutes an efficient and energy-saving alternative having the possibility of simple substitution. Any power range, whether with or without additionally required electronics, with part electronics or with full electronics, can be covered by the blower according to the invention. In this case, possible different gradings of the electronic modules can be adapted to the different air powers of the blower.